[LLVMdev] include/Config/config.h discrepancies between CMake and autofoo builds

[Óscar Fuentes]

Ruben Van Boxem <vanboxem.ruben at gmail.com> writes:

> Yeah that's the two different ones I mean. Everything MS (intrinsics,
> language features etc...) is purely version-bound, so I don't even get
> why CMake insists on checking every known function prototype of for
> example "recv" and for the presence of headers it (or the project
> dev!) should know are not there.

The fact that a given function is present on one version of VC++/MinGW
does not mean that it is present on another future or past version. The
same could be said for the Unix case. Hard-coding that information
defeats the purpose of platform checks.

We could hard-code some check results with 

if( NOT WIN32 )
  checks
elseif( MINGW )
  hard_coded_results_mingw
else
  hard_coded_results_vc
endif()

but that adds noise and increases fragility and maintenance effort. For
just saving two or three minutes while configuring, something that most
people don't do often (except if you are one of the build maintainers,
of course ;-)

> As for 3rdparty libraries: provide an option like autotools (about the
> only thing (sometimes) done right) "--with-3rdpartylibname=somePath".
> Leave it to the user/builder to get their setup right and provide the
> correct library (location)

This is not so easy. The user can replace anything you can imagine
of. From the compiler itself to core OS functionality. IIRC there are
cases of people using a third-party C standard library implementation.

[snip]